The present invention relates to a pressurized fluid fixture support system for machine tool and other environments, and in particular to a power translation and rotation apparatus wherein the fixture may be automatically translated from one position to another on the table and automatically rotated about one or more selected centers of rotation on the table.
The machining of large workpieces often involves very difficult positioning and repositioning of the workpiece when various portions thereof are machined. In many cases, it is necessary to use hoists for elevating and moving the workpiece both to and from the machine tool table, and on the table itself where repositioning is necessary for sequential machining steps.
In order to overcome these problems an air-float system, wherein the workpiece is mounted to a fixture which in turn is supported on a cushion of pressurized air, has been developed. This system is described in detail in U.S. Pat. No. 4,058,885 in the name of Raymond A. Bergman, which patent is incorporated herein by reference. In the system, a table is provided with fluid passages and a plurality of fluid outlets distributed over the surface of the table so that a cushion of pressurized air may be provided underneath the workpiece fixture. By virtue of the fluid pressure cushion, substantially friction-free movement of the fixture on the table is possible, thereby allowing positioning and repositioning to be accomplished by a single operator without the need for hoisting equipment.
However, a major inconvenience and a time consuming procedure exists with the above system in that the operator must manually translate and rotate the fixture relative to the machine tool. This inconvenient and time consuming procedural step is partially remedied by an air float power translation system wherein the workpiece is engaged by a retractable pin within the air-float table, and then translated to a new position by means of a mechanical driving system such as a hydraulic ram or feed screw. This system is described in detail in U.S. application Ser. No. 966,072 by Raymond A. Bergman, filed Dec. 4, 1978, now U.S. Pat. No. 4,354,796, the disclosure of which is hereby incorporated by reference. Specifically, U.S. application Ser. No. 966,072 provides a power translation apparatus comprising an elongated slot in the table surface, a carriage mounted in the table below the table surface for reciprocal movement parallel to the table surface along a slot, a translation pin member carried by the carriage and protruding through the slot above the surface of the table, means for selectively retracting the pin member below the table surface, and a driving mechanism for translating the carriage and pin member carried thereby along the slot.
The remaining problem above, the requirement of manually rotating the fixture, is overcome by an air float power rotation system wherein the workpiece fixture may be automatically rotated about one or more selected centers of rotation on the table. The air float power rotation system has been fully described in U.S. Pat. No. 4,298,307, the disclosure of which is hereby incorporated by reference. Specifically, U.S. Pat. No. 4,298,307 provides a table having a plurality of retractable locating pins positioned at precisely determined locations, and which selectively interengage with corresponding openings in the lower surface of the workpiece fixture so as to accurately lock the fixture in place. Preferably, the pin is square-sided in shape and engages a complementary shaped opening in the lower surface of the fixture and means are provided in the table for turning the square-sided pin about a vertical axis, whereby the fixture, which is supported on a cushion of pressurized fluid, is rotated in unison with the pin to the desired location. Furthermore, in order to provide for the rotation of the fixture about different centers of rotation, as would be the case where fixtures of different sizes are used, a plurality of automatically rotated pins may be provided in the table.
As described above, each of the references individually overcomes a portion of the total requirement of manually translating and rotating a fixture on a table for machine tooling. Consequently, each has its own individual disadvantage in that U.S. application Ser. No. 966,072 requires manually rotating the fixture, while U.S. Pat. No. 4,298,307 requires manually translating the fixture.